Wednesday, August 22, 2012
Single Image HDR: RAW to TIFF to HDR Efex Pro 2
Using the bracket shots has several advantages: 1. to avoid the clipping of over-exposed high-light; 2. to avoid the excess noise of the under-exposed shadow. However, in some occasion, with the modern digital camera, the sensor has already very wide dynamic range that can capture the whole dynamic range of the scene. How to get the most out from the this dynamic range needs some manipulations.
Direct import one single RAW file into HDR Efex Pro 2 in order to use the tools available to boost up the image has several disadvantages: 1. we lost the Auto Distortion and Auto Lateral Color Aberration; 2. we lost the Exposure Compensation. These functions are normally built in some of the RAW conversion program, Capture NX2, ACR, etc. Not all the third party software that has all the distortion profile for all the Nikon camera and lens combination. The same is for the color fringe (Lateral Color Aberration). The newer Nikon camera and the Capture NX2 software can do it easily and perfectly, no one knows better than Nikon of their own cameras and lenses. The functions only work when the RAW file is converted into JPEG or TIFF. Of cause, if you are not a Nikon user, you will have to relay on Photoshop, etc to do it for you.
As for the exposure compensation, the RAW file has way more information in it than the simple histogram can tell. When the RAW file of the above image was directly import into HDR Efex Pro 2, There is no detail in the brighter area of the sky. It was almost impossible to bring it out using global image adjustment. I know the information is in there, since if I move the exposure compensation to -2 in the Capture NX2, I got every detail out from the sky. Here is my workflow for this image:
1. Open the RAW file in Capture NX2, change Picture Control to Neutral. In the Advance tap, move all the slider to lowest: Sharpening 0, Contrast -3, Brightness -3, Saturation -3, Hue -3; 2. Leave Auto Distortion and Auto Lateral Color Aberration on.
2. Change Exposure Compensation to -2, -1, 0, +1, +2, at each setting save a file in TIFF.
3. Open all 5 TIFF files in HDR Efex Pro 2, merge them into HDR then do the adjustments.
4. Smart Sharpen the HDR image in Photoshop.
5. Adjust the orientation and prospective of the image in PTLens.
6. Final crop and adjustment in Capture NX2.
Although the ideal condition would be to have bracket shots for the original scene, but the moving canoe made it not practical for merging the shots together without "ghost effect".